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Christopher L. Brace – One of the best experts on this subject based on the ideXlab platform.

  • Analysis of iodinated contrast delivered during thermal Ablation: is material trapped in the Ablation zone?
    Physics in medicine and biology, 2016
    Co-Authors: Christopher L. Brace
    Abstract:

    Intra-procedural contrast-enhanced CT (CECT) has been proposed to evaluate treatment efficacy of thermal Ablation. We hypothesized that contrast material delivered concurrently with thermal Ablation may become trapped in the Ablation zone, and set out to determine whether such an effect would impact Ablation visualization. CECT images were acquired during microwave Ablation in normal porcine liver with: (A) normal blood perfusion and no iodinated contrast, (B) normal perfusion and iodinated contrast infusion or (C) no blood perfusion and residual iodinated contrast. Changes in CT attenuation were analyzed from before, during and after Ablation to evaluate whether contrast was trapped inside of the Ablation zone. Visualization was compared between groups using post-Ablation contrast-to-noise ratio (CNR). Attenuation gradients were calculated at the Ablation boundary and background to quantitate Ablation conspicuity. In Group A, attenuation decreased during Ablation due to thermal expansion of tissue water and water vaporization. The Ablation zone was difficult to visualize (CNR  =  1.57  ±  0.73, boundary gradient  =  0.7  ±  0.4 HU mm(-1)), leading to Ablation diameter underestimation compared to gross pathology. Group B Ablations saw attenuation increase, suggesting that iodine was trapped inside the Ablation zone. However, because the normally perfused liver increased even more, Group B Ablations were more visible than Group A (CNR  =  2.04  ±  0.84, boundary gradient  =  6.3  ±  1.1 HU mm(-1)) and allowed accurate estimation of the Ablation zone dimensions compared to gross pathology. Substantial water vaporization led to substantial attenuation changes in Group C, though the Ablation zone boundary was not highly visible (boundary gradient  =  3.9  ±  1.1 HU mm(-1)). Our results demonstrate that despite iodinated contrast being trapped in the Ablation zone, Ablation visibility was highest when contrast is delivered intra-procedurally. Therefore, CECT may be feasible for real-time thermal Ablation monitoring.

  • Evaluation of a Thermoprotective Gel for Hydrodissection During Percutaneous Microwave Ablation: In Vivo Results
    CardioVascular and Interventional Radiology, 2015
    Co-Authors: Anna J. Moreland, Fred T. Lee, Meghan G. Lubner, Timothy J. Ziemlewicz, Douglas R. Kitchin, J. Louis Hinshaw, Alexander D. Johnson, Christopher L. Brace
    Abstract:

    Purpose To evaluate whether thermoreversible poloxamer 407 15.4 % in water (P407) can protect non-target tissues adjacent to microwave (MW) Ablation zones in a porcine model. Materials and Methods MW Ablation antennas were placed percutaneously into peripheral liver, spleen, or kidney (target tissues) under US and CT guidance in five swine such that the expected Ablation zones would extend into adjacent diaphragm, body wall, or bowel (non-target tissues). For experimental Ablations, P407 (a hydrogel that transitions from liquid at room temperature to semi-solid at body temperature) was injected into the potential space between target and non-target tissues, and the presence of a gel barrier was verified on CT. No barrier was used for controls. MW Ablation was performed at 65 W for 5 min. Thermal damage to target and non-target tissues was evaluated at dissection. Results Antennas were placed 7 ± 3 mm from the organ surface for both control and gel-protected Ablations ( p  = 0.95). The volume of gel deployed was 49 ± 27 mL, resulting in a barrier thickness of 0.8 ± 0.5 cm. Ablations extended into non-target tissues in 12/14 control Ablations (mean surface area = 3.8 cm^2) but only 4/14 gel-protected Ablations (mean surface area = 0.2 cm^2; p  = 0.0005). The gel barrier remained stable at the injection site throughout power delivery. Conclusion When used as a hydrodissection material, P407 protected non-targeted tissues and was successfully maintained at the injection site for the duration of power application. Continued investigations to aid clinical translation appear warranted.

  • Computational modelling of microwave tumour Ablations.
    International Journal of Hyperthermia, 2013
    Co-Authors: Jason Chiang, Peng Wang, Christopher L. Brace
    Abstract:

    Microwave tissue heating is being increasingly utilised in several medical applications, including focal tumour Ablation, cardiac Ablation, haemostasis and resection assistance. Computational modelling of microwave Ablations is a precise and repeatable technique that can assist with microwave system design, treatment planning and procedural analysis. Advances in coupling temperature and water content to electrical and thermal properties, along with tissue contraction, have led to increasingly accurate computational models. Developments in experimental validation have led to broader acceptability and applicability of these newer models. This review will discuss the basic theory, current trends and future direction of computational modelling of microwave Ablations.

David L Ross – One of the best experts on this subject based on the ideXlab platform.

W Chik – One of the best experts on this subject based on the ideXlab platform.

  • high spatial resolution thermal mapping of radiofrequency Ablation lesions using a novel thermochromic liquid crystal myocardial phantom
    Journal of Cardiovascular Electrophysiology, 2013
    Co-Authors: W Chik, David L Ross, M A Barry, Sujitha Thavapalachandran, Christine Midekin, Jim Pouliopoulos, Gopal Sivagangabalan, Stuart P Thomas
    Abstract:

    BACKGROUND: Radiofrequency (RF) Ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF Ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro Ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF Ablations were performed. This comprised 17 Ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo Ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo Ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be <300 μm. CONCLUSIONS: High spatial resolution thermal mapping of in vitro RF lesions with spatial resolution of at least 300 μm is possible using a thermochromic liquid crystal myocardial phantom model, with a good correlation to in vivo RF Ablations. This model may be useful for assessing the thermal characteristics of RF lesions created using different Ablation parameters and catheter technologies.

  • High Spatial Resolution Thermal Mapping of Radiofrequency Ablation Lesions Using a Novel Thermochromic Liquid Crystal Myocardial Phantom
    Journal of Cardiovascular Electrophysiology, 2013
    Co-Authors: W Chik, David L Ross, M A Barry, Sujitha Thavapalachandran, Christine Midekin, Jim Pouliopoulos, Gopal Sivagangabalan, Stuart P Thomas, Alistair Mcewan
    Abstract:

    BACKGROUND: Radiofrequency (RF) Ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF Ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro Ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF Ablations were performed. This comprised 17 Ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo Ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo Ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be

  • High Spatial Resolution Thermal Mapping of Radiofrequency Ablation Lesions Using a Novel Thermochromic Liquid Crystal Myocardial Phantom
    Journal of cardiovascular electrophysiology, 2013
    Co-Authors: W Chik, David L Ross, M A Barry, Sujitha Thavapalachandran, Christine Midekin, Jim Pouliopoulos, Gopal Sivagangabalan, Stuart P Thomas, Toon Wei Lim, Alistair Mcewan
    Abstract:

    High-Resolution Thermal Mapping of RF Ablation LesionsBackground Radiofrequency (RF) Ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF Ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro Ablation lesions. Methods and Results The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF Ablations were performed. This comprised 17 Ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo Ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo Ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be

Alistair Mcewan – One of the best experts on this subject based on the ideXlab platform.

  • High Spatial Resolution Thermal Mapping of Radiofrequency Ablation Lesions Using a Novel Thermochromic Liquid Crystal Myocardial Phantom
    Journal of Cardiovascular Electrophysiology, 2013
    Co-Authors: W Chik, David L Ross, M A Barry, Sujitha Thavapalachandran, Christine Midekin, Jim Pouliopoulos, Gopal Sivagangabalan, Stuart P Thomas, Alistair Mcewan
    Abstract:

    BACKGROUND: Radiofrequency (RF) Ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF Ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro Ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF Ablations were performed. This comprised 17 Ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo Ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo Ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be

  • High Spatial Resolution Thermal Mapping of Radiofrequency Ablation Lesions Using a Novel Thermochromic Liquid Crystal Myocardial Phantom
    Journal of cardiovascular electrophysiology, 2013
    Co-Authors: W Chik, David L Ross, M A Barry, Sujitha Thavapalachandran, Christine Midekin, Jim Pouliopoulos, Gopal Sivagangabalan, Stuart P Thomas, Toon Wei Lim, Alistair Mcewan
    Abstract:

    High-Resolution Thermal Mapping of RF Ablation LesionsBackground Radiofrequency (RF) Ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF Ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro Ablation lesions. Methods and Results The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF Ablations were performed. This comprised 17 Ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo Ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo Ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be

Jim Pouliopoulos – One of the best experts on this subject based on the ideXlab platform.

  • renal artery branch denervation evaluation of lesion characteristics using a thermochromic liquid crystal phantom model
    Heart Lung and Circulation, 2020
    Co-Authors: Sara I. Al Raisi, Jim Pouliopoulos, Pramesh Kovoor, M. Barry, Pierre Qian, Aravinda Thiagalingam, John Swinnen
    Abstract:

    Background Lately, combined main vessel and branch Ablation has been recommended during radiofrequency (RF) renal arteartery denervation. Utilising a validated renal arteartery phantom model, we aimed (1) to determine thermal injury extent (lesion depth, width and circumferential coverage) and electrode-tissue interface temperature for branch renal arteartery Ablation, and (2) to compare the extent of thermal injury for branch versus main vessel Ablation using the same RF System. Methods We employed a gel based renal arteartery phantom model simulating variable vessel diameter and flow, which incorporated a temperature sensitive thermochromic-liquid-crystal (TLC) film for assessing RF Ablation thermodynamics. Ablations in a branch renal arteartery model (n = 32) were performed using Symplicity Spyral (Medtronic, Minneapolis, MN, USA). Lesion dimensions defined by the 51 °C isotherm, circumferential injury coverage, and electrode-tissue interface temperature were measured for all Ablations at 60 seconds. Results Lesion dimensions were 2.13 ± 0.13 mm and 4.13 ± 0.18 mm for depth and width, respectively, involving 23% of the vessel circumference. Maximum electrode-tissue interface temperature was 68.31 ± 2.29 °C. No significant difference in lesion depth between branch and main vessel Ablations was found (Δ = 0.02 mm, p = 0.60). However, lesions were wider in the branch (Δ=0.49 mm, p  Conclusions In the phantom model, branch Ablations were of similar depth but had larger width and circumferential coverage compared to main vessel Ablations. Concerning safety, no overheating at the electrode-tissue interface was observed.

  • high spatial resolution thermal mapping of radiofrequency Ablation lesions using a novel thermochromic liquid crystal myocardial phantom
    Journal of Cardiovascular Electrophysiology, 2013
    Co-Authors: W Chik, David L Ross, M A Barry, Sujitha Thavapalachandran, Christine Midekin, Jim Pouliopoulos, Gopal Sivagangabalan, Stuart P Thomas
    Abstract:

    BACKGROUND: Radiofrequency (RF) Ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF Ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro Ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF Ablations were performed. This comprised 17 Ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo Ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo Ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be <300 μm. CONCLUSIONS: High spatial resolution thermal mapping of in vitro RF lesions with spatial resolution of at least 300 μm is possible using a thermochromic liquid crystal myocardial phantom model, with a good correlation to in vivo RF Ablations. This model may be useful for assessing the thermal characteristics of RF lesions created using different Ablation parameters and catheter technologies.

  • High Spatial Resolution Thermal Mapping of Radiofrequency Ablation Lesions Using a Novel Thermochromic Liquid Crystal Myocardial Phantom
    Journal of Cardiovascular Electrophysiology, 2013
    Co-Authors: W Chik, David L Ross, M A Barry, Sujitha Thavapalachandran, Christine Midekin, Jim Pouliopoulos, Gopal Sivagangabalan, Stuart P Thomas, Alistair Mcewan
    Abstract:

    BACKGROUND: Radiofrequency (RF) Ablation causes thermal mediated irreversible myocardial necrosis. This study aimed to (i) characterize the thermal characteristics of RF Ablation lesions with high spatial resolution using a thermochromic liquid crystal (TLC) myocardial phantom; and (ii) compare the thermochromic lesions with in vivo and in vitro Ablation lesions. METHODS AND RESULTS: The myocardial phantom was constructed from a vertical sheet of TLC film, with color change between 50 °C (red) to 78 °C (black), embedded within a gel matrix, with impedance titrated to equal that of myocardium. Saline, with impedance titrated to blood values at 37 °C, was used as supernatant. A total of 51 RF Ablations were performed. This comprised 17 Ablations in the thermochromic gel phantom, bovine myocardial in vitro targets and ovine in vivo Ablations, respectively. There was no difference in lesion dimensions between the thermochromic gel and in vivo Ablations (lesion width 10.2 ± 0.2 vs 10.2 ± 2.4, P = 0.93; and depth 6.3 ± 0.1 vs 6.5 ± 1.7, P = 0.74). The spatial resolution of the thermochromic film was tested using 2 thermal point-sources that were progressively opposed and was demonstrated to be